Support control links for non-js users

The controls option (Prev/Next) and the pager option (e.g., 1 2 3) should properly degrade for non-js users but does not -- it simply hides these and displays only the first item in the slideshow. This means that the slideshow doesn't work at all for non-js users -- even putting aside all bells and whistles, at least these simple controls should degrade properly.

Attached patch adds this functionality, without affecting the js version.